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<h1 class="entry-title">.eq()</h1>
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						所属分类：<span class="category"><a href="/category/traversing/">遍历</a> &gt; <a href="/category/traversing/filtering/">过滤</a></span>
<span class="pull-right">英文文档：<a href="https://api.jquery123.com/eq/" target="_blank">.eq()</a></span>
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<article class="entry method" id="eq1"><h2 class="section-title">
<span class="name">.eq( index )</span><span class="returns">返回: <a href="/Types/#jQuery">jQuery</a></span>
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<p class="desc"><strong>描述: </strong>减少匹配元素的集合为指定的索引的哪一个元素。</p>
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<li class="signature" id="eq-index">
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<span class="version-details">添加的版本: <a href="/category/version/1.1.2/">1.1.2</a></span>.eq( index )</h4>
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<div><strong>index</strong></div>
<div>类型: <a href="/Types/#Integer">Integer</a>
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<div>一个整数，指示元素的位置，以0为基数。</div>
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<li class="signature" id="eq--index">
<h4 class="name">
<span class="version-details">添加的版本: <a href="/category/version/1.4/">1.4</a></span>.eq( -index )</h4>
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<div><strong>-index</strong></div>
<div>类型: <a href="/Types/#Integer">Integer</a>
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<div>一个整数，指示元素的位置，从集合中的最后一个元素开始倒数。</div>
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<p>如果一个jQuery对象表示一个DOM元素的集合，<code>.eq()</code>方法从集合的一个元素中构造新的jQuery对象。所提供的索引标识这个集合中的元素的位置。 </p>
<p>考虑一个页面上一个简单的列表：</p>
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<table>
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<td class="gutter">
<div class="line n1">1</div>
<div class="line n2">2</div>
<div class="line n3">3</div>
<div class="line n4">4</div>
<div class="line n5">5</div>
<div class="line n6">6</div>
<div class="line n7">7</div>
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<pre><div class="container"><div class="line"><code>  <span class="tag">&lt;<span class="title">ul</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>    <span class="tag">&lt;<span class="title">li</span>&gt;</span>list item 1<span class="tag">&lt;/<span class="title">li</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>    <span class="tag">&lt;<span class="title">li</span>&gt;</span>list item 2<span class="tag">&lt;/<span class="title">li</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>    <span class="tag">&lt;<span class="title">li</span>&gt;</span>list item 3<span class="tag">&lt;/<span class="title">li</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>    <span class="tag">&lt;<span class="title">li</span>&gt;</span>list item 4<span class="tag">&lt;/<span class="title">li</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>    <span class="tag">&lt;<span class="title">li</span>&gt;</span>list item 5<span class="tag">&lt;/<span class="title">li</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>  <span class="tag">&lt;/<span class="title">ul</span>&gt;</span></code></div></div></pre>
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<p>我们可以在列表项目上设置此方法：
			
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<tr>
<td class="gutter">
<div class="line n1">1</div>
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<pre><div class="container"><div class="line"><code>  $(<span class="string">'li'</span>).eq(<span class="number">2</span>).css(<span class="string">'background-color'</span>, <span class="string">'red'</span>);</code></div></div></pre>
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<p>此调用的结果是item 3的背景变成红色。请注意，提供的索引是从0开始的，代表元素在jQuery对象中的位置，而不是在DOM树中的位置。</p>
<p>提供一个负数表示的元素的位置从集合中的末尾开始，而不是开头。例如：</p>
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<td class="gutter">
<div class="line n1">1</div>
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<pre><div class="container"><div class="line"><code>  $(<span class="string">'li'</span>).eq(-<span class="number">2</span>).css(<span class="string">'background-color'</span>, <span class="string">'red'</span>);</code></div></div></pre>
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<p>这一次清单item 4变成了红色，因为这是从集合的末尾开始的第二个。</p>
<p>如果指定索引位置的元素不存在，该方法构造了一个空的新jQuery对象，<code>length</code>属性值是0。 </p>
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<div class="line n1">1</div>
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<pre><div class="container"><div class="line"><code>  $(<span class="string">'li'</span>).eq(<span class="number">5</span>).css(<span class="string">'background-color'</span>, <span class="string">'red'</span>);</code></div></div></pre>
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<p>在这里，列表项都没有变成了红色。<code>.eq(5)</code>表示5个项的list的第六个元素，没有啊，亲！</p>
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<section class="entry-examples" id="entry-examples"><header><h2 class="underline">例子:</h2></header><div class="entry-example" id="example-0">
<h4><span class="desc">为索引值是为 2 的 div 添加适当的 class，将其变成蓝色。</span></h4>
<div class="syntaxhighlighter xml ">
<table>
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<td class="gutter">
<div class="line n1">1</div>
<div class="line n2">2</div>
<div class="line n3">3</div>
<div class="line n4">4</div>
<div class="line n5">5</div>
<div class="line n6">6</div>
<div class="line n7">7</div>
<div class="line n8">8</div>
<div class="line n9">9</div>
<div class="line n10">10</div>
<div class="line n11">11</div>
<div class="line n12">12</div>
<div class="line n13">13</div>
<div class="line n14">14</div>
<div class="line n15">15</div>
<div class="line n16">16</div>
<div class="line n17">17</div>
<div class="line n18">18</div>
<div class="line n19">19</div>
<div class="line n20">20</div>
<div class="line n21">21</div>
<div class="line n22">22</div>
<div class="line n23">23</div>
<div class="line n24">24</div>
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<pre><div class="container"><div class="line"><code><span class="doctype">&lt;!DOCTYPE html&gt;</span></code></div></div><div class="container"><div class="line"><code><span class="tag">&lt;<span class="title">html</span>&gt;</span></code></div></div><div class="container"><div class="line"><code><span class="tag">&lt;<span class="title">head</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>  <span class="tag">&lt;<span class="title">style</span>&gt;</span><span class="css"></span></code></div></div><div class="container"><div class="line"><code>  <span class="tag">div</span> <span class="rules">{ <span class="rule"><span class="attribute">width</span>:<span class="value"><span class="number">60</span>px;</span></span> <span class="rule"><span class="attribute">height</span>:<span class="value"><span class="number">60</span>px;</span></span> <span class="rule"><span class="attribute">margin</span>:<span class="value"><span class="number">10</span>px;</span></span> <span class="rule"><span class="attribute">float</span>:<span class="value">left;</span></span></span></code></div></div><div class="container"><div class="line"><code>        <span class="rule"><span class="attribute">border</span>:<span class="value"><span class="number">2</span>px solid blue;</span></span> <span class="rule">}</span></code></div></div><div class="container"><div class="line"><code>  <span class="class">.blue</span> <span class="rules">{ <span class="rule"><span class="attribute">background</span>:<span class="value">blue;</span></span> <span class="rule">}</span></span></code></div></div><div class="container"><div class="line"><code>  <span class="tag">&lt;/<span class="title">style</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>  <span class="tag">&lt;<span class="title">script</span> <span class="attribute">src</span>=<span class="value">"https://code.jquery.com/jquery-latest.js"</span>&gt;</span><span class="javascript"></span><span class="tag">&lt;/<span class="title">script</span>&gt;</span></code></div></div><div class="container"><div class="line"><code><span class="tag">&lt;/<span class="title">head</span>&gt;</span></code></div></div><div class="container"><div class="line"><code><span class="tag">&lt;<span class="title">body</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>  <span class="tag">&lt;<span class="title">div</span>&gt;</span><span class="tag">&lt;/<span class="title">div</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>  <span class="tag">&lt;<span class="title">div</span>&gt;</span><span class="tag">&lt;/<span class="title">div</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>  <span class="tag">&lt;<span class="title">div</span>&gt;</span><span class="tag">&lt;/<span class="title">div</span>&gt;</span></code></div></div><div class="container"><div class="line"><code> </code></div></div><div class="container"><div class="line"><code>  <span class="tag">&lt;<span class="title">div</span>&gt;</span><span class="tag">&lt;/<span class="title">div</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>  <span class="tag">&lt;<span class="title">div</span>&gt;</span><span class="tag">&lt;/<span class="title">div</span>&gt;</span></code></div></div><div class="container"><div class="line"><code>  <span class="tag">&lt;<span class="title">div</span>&gt;</span><span class="tag">&lt;/<span class="title">div</span>&gt;</span></code></div></div><div class="container"><div class="line"><code><span class="tag">&lt;<span class="title">script</span>&gt;</span><span class="javascript"></span></code></div></div><div class="container"><div class="line"><code>$(<span class="string">"body"</span>).find(<span class="string">"div"</span>).eq(<span class="number">2</span>).addClass(<span class="string">"blue"</span>);</code></div></div><div class="container"><div class="line"><code><span class="tag">&lt;/<span class="title">script</span>&gt;</span></code></div></div><div class="container"><div class="line"><code> </code></div></div><div class="container"><div class="line"><code><span class="tag">&lt;/<span class="title">body</span>&gt;</span></code></div></div><div class="container"><div class="line"><code><span class="tag">&lt;/<span class="title">html</span>&gt;</span></code></div></div></pre>
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<h4>Demo:</h4>
<div class="demo code-demo"></div>
</div></section>
</div></article> </div>
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